An industrial railroad siding where hazardous chemicals are loaded and unloaded from rail tank cars presents an environmental concern, in that an accidental spill of some or all of the contents of the rail tank car can occur. Typically, such spills can be divided into “nuisance spills,” where a small quantity of chemicals escape the tank car during the connection or disconnection of hoses or from leaks in the hoses of the unloading system, and “catastrophic spills,” where a hose ruptures or valve or coupling gives way and the entire contents of the tank car are released. A rail tank car may contain from 16,000 to 40,000 gallons of chemical and may have up to a 5″ or larger discharge opening. In the event of a catastrophic spill, this volume of chemical may be rapidly released onto the rail bed and could quickly find its way into nearby streams or ground water. This could result in significant environmental damage, a costly cleanup, and stiff regulatory fines.
A common precaution in these situations is to install a containment system underneath the rail tank cars to capture any liquids spilled during loading and unloading, such as a series of catch pans installed on the rail bed between the rails of the siding. Typical catch pan systems, while perhaps adequate to contain most nuisance spills, cannot safely contain a catastrophic spill of a hazardous chemical. Typical catch pan system designs generally require each pan to have its own means for drainage, and these drains are usually not sufficiently large to handle the volume and rate of liquid being discharged from the typical discharge opening of a tank car, such as a 5″ discharge opening. If the drain for a particular pan becomes blocked or overwhelmed by the flow rate liquid, the pan can quickly fill and potentially overflow onto the rail bed underneath.